A problem with a conventional on-vehicle guidance apparatus is that because it always keeps the output sound volume of guidance outputted from a speaker constant even though conditions in a cabin are varying variously, when the user is watching a sport or listening rock music with onboard equipment, such as a TV (Television), a radio, or audio equipment, he or she fails to listen important guidance. To solve this problem, there has been provided a conventional on-vehicle guidance having a microphone for acquiring an output sound of onboard equipment at a location where the sound of the onboard equipment is outputted, for automatically changing the output sound volume of guidance according to the sound volume of the output sound acquired by the above-mentioned microphone (e.g., refer to patent reference 1).    [Patent reference 1] JP, 11-55055,A
A problem with the conventional on-vehicle guidance apparatus is that because it only changes the sound volume of guidance, and outputs guidance with an always-fixed description and an always-fixed voice impersonation, when the atmosphere in the cabin is coming alive, such as when the user is watching a sport or listening rock music with onboard equipment, such as a TV (Television), a radio, or audio equipment, the conventional on-vehicle guidance apparatus suddenly outputs guidance with a quiet and calm voice impersonation, and therefore puts a damper on the good atmosphere. A further problem is that because the conventional on-vehicle guidance apparatus changes the output sound volume of guidance according to the sound volume of an output sound from onboard equipment, and does not take into consideration another environmental sound in the cabin, passengers fail to catch important guidance when the atmosphere in the cabin is coming alive.
The present invention is made in order to solve the above-mentioned problems, and it is therefore an object of the present invention to provide an on-vehicle guidance apparatus that can prevent passengers from failing to catch important guidance by determining the time of outputting guidance in such a way that the time is suitable for the situation.